Phylum Rotifera includes microscopic multicellular aquatic organisms characterized by a wheel-like corona structure. They reproduce through parthenogenesis or sexually. Phylum Nematoda includes roundworms with bilaterally symmetrical cylindrical bodies. They are free-living or parasitic. Major nematode orders include Rhabditida, Strongylida, Oxyurida, and Ascaridida. Some nematode infections in humans are ascariasis, trichuriasis, enterobiasis, filariasis, and trichinosis.

1. PHYLUM ROTIFERA AND PHYLUM
NEMATODA
Lecture-6
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2. Phylum Rotifera
1. The rotifers are microscopic, (about 100 µm
to 30 mm) multicellular, mostly aquatic
organisms that are currently under taxonomic
revision.
2. The group is characterized by the rotating,
ciliated, wheel-like structure, the corona, on
their head.
3. The mastax or jawed pharynx is another
structure unique to this group of organisms.
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3. Characteristics
• Etymology-
• From the Latin Rota a wheel, and Ferre to bear or carry.
Characteristics of Rotifera:
• Bilaterally symmetrical.
• Body has more than two cell layers, tissues and organs.
• Body cavity is a pseudocoelom.
• Body possesses a through gut with an anus.
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4. • Body covered in an external layer of chitin called a lorica.
• Has a nervous system with a brain and paired nerves.
• Has no circulatory or respiratory organs.
• Reproduction mostly parthenogenetic, otherwise sexual and gonochoristic.
• Feed on bacteria, and protista, or are parasitic.
• All live in aquatic environments either free swimming or attached.
Phylum Rotifera
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5. • About 2,200 species of rotifers have been identified.
• Rotifers are dioecious organisms (having either male or female genitalia) and
exhibit sexual dimorphism (males and females have different forms).
• In many dioecious species, males are short-lived and smaller with no digestive
system and a single testis.
• Females can produce eggs that are capable of dormancy for protection during harsh
environmental conditions.
Characteristics
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6. Rotifers-Morphology
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7. Euchlanis
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8. Common Representatives
Conochilus
Found in clean lakes and pounds and in colonies).
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9. Asplanchna
Found in the Great Lakes
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10. Brachionus
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11. Phylum Nematoda- Characteristics
• Their body is bilaterally symmetrical and triploblastic.
• They are cylindrical in shape.
• They exhibit tissue level organization.
• Their body has a cavity or pseudocoelom.
• The alimentary canal is distinct, with the mouth and the anus.
• They are sexually dimorphic.
• They are devoid of the circulatory system and respiratory system.
• The phylum Nematoda, also known as the roundworms, is the second largest
phylum in the animal kingdom, encompassing up to 500,000 species.
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13. Phylum Nematoda-Characteristics
• They are free-living or parasitic.
• Parasitic nematodes cause diseases in the host.
• Fertilization is internal and reproduction is sexual.
• Their cuticle moults periodically.
• The epidermis is synctical and contains dorsal or ventral nerve cords.
• The body-wall muscles are longitudinal.
• They possess amoeboid sperm cells.
• They consist of chemosensory organs called aphids situated on the lips.
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14. Rhabditida
• They have smooth and ringed cuticle.
• There is a posterior lobe at the pharynx.
• They are free-living and parasitic.
• Males have copulatory spicules.
• Eg., Rhabditis
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15. Strongylida
• They are vertebrate parasites devoid of lips.
• The pharynx has no bulb.
• They have a well-developed buccal capsule.
• They possess a true copulatory bursa.
• For eg., Strongylus
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16. Oxyurida
• They can be small or moderate in size.
• Males have copulatory spicules.
• Caudal alae are present.
• They can be invertebrates or vertebrates.
• The mouth consists of 3-4 simple lips.
• For example, Oxyuris.
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17. Ascaridida
• These are oviparous, large stout nematodes living as parasites in the intestine of
the vertebrates.
• The pharynx may or may not contain a posterior bulb.
• Mouth possess 3 prominent lips.
• There is no buccal capsule.
• For eg., Ascaris
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18. Camallanida
• These are oviparous, thread-like organisms.
• The males have no bursa.
• The bursa of adult females is degenerated.
• For eg., Camallanus
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19. Infections in Humans
Some of the Nematode infections in humans include:
• Ascariasis
• Trichuriasis
• Enterobiasis
• Filariasis
• Trichinosis
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22. Trichinella Spiralis Life Cycle
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